1. Field of the Invention
This invention relates to catheters intended to be inserted into the body and, more specifically, to a catheter and method for using the same for evaluating the competency of a mitral valve during cardiac surgery.
2. Description of the Related Art
The mitral valve is positioned in the heart between the left ventricle and left atrium and controls the flow of blood from the left atrium to the left ventricle. Under normal conditions, the valve permits the flow of blood from the atrium to the ventricle as the left atrium contracts. However, as the left ventricle begins to contract, a normal operating mitral valve closes to prevent the blood from returning to the left atrium. This reverse flow is known as regurgitation. As the left ventricle contracts, blood flows through the aortic valve into the aorta for distribution throughout the body.
One form of heart disease is deterioration or degradation of the valves, such as the mitral valve. It is often preferable to repair a natural valve rather than excising the valve and replacing it with a prosthesis or replacement tissue valve. A patient having a replacement valve such as a prosthetic valve must be placed on anti-coagulant drugs for the remainder of his or her life. However, a repaired valve which does not necessarily include any prosthetics or new tissue does not require this lifelong commitment to anti-coagulant drugs. In addition, valve repair surgery is often safer and less expensive than implantation of a prosthetic valve or tissue. In general, mitral valve repair preserves left ventricular function better than mitral valve replacement because during repair, the subvalvular papillary muscles and chordae tendineae are preserved whereas during mitral valve replacement, they cannot always be preserved in their natural orientation. Therefore, valve repair is often more desirable than replacement.
A significant concern for surgeons performing repairs of valves such as the mitral valve is confirming the competency of the valve repair prior to removing the patient from cardiac bypass. One known technique for evaluating the competency of a repaired mitral valve is to insert a catheter through the mitral valve and inject a suitable fluid, such as saline, into the left ventricle. The catheter is removed and the surgeon observes the competency of the valve. The surgeon can directly view the valve through the typical access aperture created in the heart wall for performing the mitral valve repair or replacement, namely, a surgical incision cut into the left atrium. One problem with this valve testing technique is the creation of insufficient fluid pressure within the ventricle to confidently evaluate the performance of the valve. In addition, this technique also requires insertion of the catheter through the mitral valve which can also distort the valve performance.
Another known technique for evaluating the competency of a repaired mitral valve is to create an incision in the left ventricle and insert one end of a catheter therethrough. A suitable fluid is injected, under pressure, into the left ventricle as the surgeon observes the competency of the mitral valve through the surgical access aperture created in the left atrium. A significant problem with this procedure is creating yet another incision in the wall of the heart. Any incision of the left ventricle is to be avoided because of potential healing problems in view of the significant fluid pressures naturally occurring inside this chamber.